How do I create a Smooth Material for my Model?
Use smooth shading on the geometry of the object
Use a subsurface modifier to make sure there are no remaining sharp edges
Use a high roughness value, like 0.8 or higher
Use subsurface scattering to give it a plastic look, as if some light is passing through thinner sections, but this is optional
Use a large light source/lamp that won't cast sharp shadows.